Re: [PATCH 3/4] drm/i915: Cache sink_count for eDP

[Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>]

On Fri, 2018-10-05 at 16:35 -0700, José Roberto de Souza wrote:
> For eDP panels all the DPCD and EDID data is cached when initializing
> the eDP connector so in futher detection it do not call
> intel_dp_detect_dpcd() for eDP.
> The problem is on the first short pulse interruption it calls
> intel_dp_get_dpcd() for eDP and DP and it will read and set the sink
> count, causing a mismatch between old sink count and the new one
> triggering a full detection without needed.
> 
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index 19f0c3f59cbe..4a1c31ec9065 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3926,6 +3926,7 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>  {
>  	struct drm_i915_private *dev_priv =
>  		to_i915(dp_to_dig_port(intel_dp)->base.base.dev);
> +	u8 val;
>  
>  	/* this function is meant to be called only once */
>  	WARN_ON(intel_dp->dpcd[DP_DPCD_REV] != 0);
> @@ -3997,6 +3998,10 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
>  
>  	intel_dp_set_common_rates(intel_dp);
>  
> +	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_SINK_COUNT, &val) <=
> 0)
> +		return false;
> +	intel_dp->sink_count = DP_GET_SINK_COUNT(val);
Is this even relevant for eDPs? Seems unnecessary to read or compare
sink count for eDP. I'd suggest skipping DP_SINK_COUNT checks for eDP.


-DK

> +
>  	return true;
>  }
>  

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